The present invention relations to systems and methods for controlling the flow of pressurized fluid and, more specifically, to a pneumatically actuated flow controller.
Many fluid flow situations exist where a flow controller is needed but does not have access to electricity or where the flow controller is situated in a hazardous, hostile and/or explosive environment. These situations require an xe2x80x9cintrinsically safexe2x80x9d flow controller. Often, to meet a standard for intrinsic safety, a flow controller must operate at very low (or absent) electrical energy.
Common prior art electronic flow controllers such as thermal, differential pressure, and Coriolis mass flow controllers employ electronic circuitry and an electromechanical valve (such as a solenoid or piezoelectric valve) to modulate or control the flow. Even though the electronic circuitry can either be remote or designed to operate within certain energy regimes, prior art flow controllers must generally use electromechanical valves that require a substantial amount of electrical energy. This generally eliminates such common prior art flow controllers from applications that require an intrinsically safe flow controller.
The need exists for an improved flow controller that meets standards for intrinsic safety.
The present invention is an intrinsically safe pneumatically actuated flow controller. A preferred embodiment for the flow controller has a housing assembly defining an inlet port, an outlet port, a pressure signal inlet port, and a main flow path extending between the inlet port and the outlet port. A restriction member is arranged in the main flow path. A first valve assembly and second valve assembly control fluid flow along the main flow path. A first regulator assembly operates the first valve assembly. A pressure signal actuation assembly has an actuation bellows attached to an actuation piston mounted on a flow control piston rod that passes through an isolation plate and is sheathed by an isolation bellows. The flow control piston rod terminates in a flow control piston that engages a second regulator assembly, which operates the second valve assembly based on pressure signals transmitted through the pressure signal inlet to the pressure signal actuation assembly.